Pallet construction for sintering apparatus



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May 23, 1951 v. F. KooNTz PALLET CONSTRUCTION FOR SINTERING APPARATUSFiled June 6, 1958 May 23, 1961 v. F. KooNTz 2,985,440

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United States Patent O PALLET CONSTRUCTION FOR SINTERING APPARATUSVictor F. Koontz, Moon Township, Allegheny County, Pa., assigner toDravo Corporation, Pittsburgh, Pa., a corporation'of Pennsylvaniav FiledJune s, 195s, ser. No. 740,317

2 claims. (ci. zas- 21) This invention relates to sintering apparatusand is for an improved pallet or tray construction for use in down draftsintering apparatus.

In down draft sintering apparatus, the pellets to be burned or sinteredare deposited on a succession of traveling trays or pallets that Imoveprogressively over a succession of suction chambers, or wind boxes, sothat the charge, after being ignited, is supplied with air drawn downthrough the charge. These trays or pallets are in reality each a smallcar rolling or sliding on rails at each end ofthe pallets, each carabutting against the one ahead to form in effect, a continuous travelingsupport. They are rectangular in shape with their greatest :lengthcrosswise of the direction of travel. They have strength membersextending in the direction of their length, whichv members are anged atthe top. A system of grate bars extending crosswise of the length of thepallet are intertted with these llanged members to support the chargewhich is to be burned.

In a typical operation, the top ilange of the supporting or strengthbars may reach a temperature of 1500 to 1900 F. while the 'bottomflanges of the same members are more nearly that f of the combustiongases Vin ythe neighborhood of l1'00to-l300 -F.

Warping of the trayswhas been a constant problem, since after a periodof use they sag from the ends toward the center. Various eforts havebeen made to correct this without success, although it has been apersistent and costly weakness. Among other things, it has been proposedto use more massive strength members. It has also been proposed to usealloys for the strength members. A further unsuccessful expedient hasbeen to provide air chambers in the strength members to lower thetemperature of the critical-ly stressed metal.

Since sagging could not be corrected, one expedient is to make themreversible and allow them to sag in one direction, turn them over, andlet them sag in the other direction. Another plan is to make them in twosections and bolt them together at the middle. When sagging occurs, thebolts are loosened and shims are used between the sections to try tocorrect warping.

I have determined that sagging is not due merely to the overheating of abeam section while under uniform load, but that by reason of thenon-linear temperature differential that exists at the top and thebottom of the beam a high stress is induced in the ilange at the topwhich supports the grate bars as it attempts to expand under the greaterheat and this expansion is restrained by the cooler metal at the bottomof the section. This results in compressive forces in the top ilangesufficient to upset or warp it, so that when the pallet cools to a pointwhere the top and bottom ilange are at equal ambient temperature, thetop is shorter than the bottom, resulting in a downward curve from theends toward the middle.

'My invention has for its principal object to provide a palletconstruction in which thermal stresses such as produce warping will beavoided. A further object of Patented May 23, 1961 my invention is toprovide a construction in which the beams will be subjected to morenearly uniform temperature at the top and bottom. A still further objectis to provide a pallet of improved construction.

vThese and other objects and advantages will be apparent to rthoseskilled in the art from the following description of my invention inconjunction with the accompanying drawings, in which:

Fig. 1 isa front elevation of one end of a pallet embodying myinvention, it being understood that the opposite end is a counterpartthereof, and for clarity of illustration only one end has been shown;

Fig. 2 is a fragmentary transverse vertical section in the plane of lineyII---II of Fig. 1 with the grate bars indicated by dot-and-dash lines;

Fig. 3 is afragmentary top plan view of an area of,

the pallet showing my invention; and

Fig. 4 is a' longitudinal vertical section in the plane of line IV--IVof Fig. 3.

Referring to the'drawings, the pallet comprises a carriage which isessentially abeam of rectangular section.

YThe arrow inFig. 2 indicates the direction of travel of the pallet. Ateach end of the carriage there is a transition plate 2 to which issecured a casting 3 that carries the shaft for supporting the wheels 4that support the pallet on the track (not shown) along which the palletmoves, the transition plate abutting against an end plate 2a. Y There'is a side plate 5 on this casting to retain the bed of material on thepallet, and 6 designates the usual seal that rides along the top of thewind boxes.

- I have shown the carriage as being fabricated fromy p tion not onlyatthe ends by the end plates 2, but at intervals along the lengthofthepallet by cross` members of I-beam section, designated 9 in Figs. 3and 4. The number of I-beams 8 and the number of cross connections 9depends upon the size of the sinteng apparatus and is not material tothe present invention, but there should be a maximum open area throughwhich combustion gases can be drawn, and it Iwill of course be apparentthat this structure could be an integral casting.

Thus the carriage comprises a composite beam of rectangular sectionformed of parallel sections connected at their ends and intermediatepoints. Bolted to the top of this composite frame are a plurality ofparallel angle sections 10, the bolts for securing them being designated11. The vertical webs 10a of these angles have horizontally elongatedslots 12 therethrough. Placed against and bolted to each of thesevertical webs 11a of the angles are the vertical webs of compositeflanged bars 13 and 14, the bars 13 being at the longitudinal side edgesof the structure and having a horizontal ilange 13a that extends towardthe longitudinal center of the structure, while the bars 14 have flanges14a that extend in both directions. The flanges 13araud 14a fit into'notches in the ends of the replaceable grate bars 15 that extend in adirection transverse to the length of the pallet, and in this mannersupport and retain the grate bars in the structure. The llanged bars 13and 14 are secured to the Vertical webs 11a of the angles by bolts 16passing through the bars Iand through the slots v12 in the verticalwebs, with nuts L16a that are taken -up firmly but not too tight. Thisprovides a friction clamp connecting ythe anged bars and the angles. v

From the foregoing it will be seen that the grate. bars,T

and 14 are separate from the bottom beam sections 7 'and'z 8respectively, forming rigid beams in which the top` can' expand andcontract independently of the bottom by reaso'n of the bolts 16 passingthrough horizontally slotted openings in one part of the compositestructure. The ends of the top bar portions 13. and 14 are not confined,so that expansion and'contraction of these portions relatively to thesupporting structure below is confined only by the tightness of thebolts and nuts 16-f-16a..v

Also there areV two boltedvconnections, one. between the bars 13 and 14,and the vertical `wehstof the angles 11, and the second between thebases of the angles 11 and the tops of the main pallet frame. Sincethese afford al poor path of heat conductivity, there istless heatcarried by conduction into the top parts of the channels7 and beams 8,and they thereforeare at a more nearly uniform temperature during thesintering of the charge on `the grates, this beingV closertothetemperature of the combustion gases. a -v By reason of thisconstruction, therefore, a pallet'is provided in which sagging andcracking is greatly reduced or entirely eliminated, thereby getting ridVof one o'f the heretofore troublesome problems encountered in apparatusof this kind. Y Y

I claim: Y

l. A pallet -for sintering machines comprising a rigid frame having liketop and bottom surfaces so that either may be used by turning it. over,the frame being of rectangular` transverse section and having two endmembers-v with spaced parallel beams connecting the end members, thespaces between thel beamsI being open for thetpassage of air through thepallet, the uppermost surface of the frame having a plurality of angleAbars releasably secured thereto with one leg of each bar supported onthe uppermost surface ofy the frame and having -one'leg'portionextendingvertically,a flanged grate-supportingl bar having a- Vertical webportion bolted to the vertical legl portion'of each of saidangle bars bybolts passingthroughthe respective vertical legportions of thegrate-supporting"4 bar and theV anglev bar, one of the leg portionsso'boltedtogether being longitudinally Vslotted for the passagev of boltstherethrough but allowing relative expansion and contraction of one legportion lengthwise, to', the other, and grates having grooved endsintertted with the flanges of the grate-supporting bars, said anges andgrates being in a plane spaced above the uppermost surface of the rigidframe.

2. A pallet for sintering machines comprising a main supporting framehaving like top and bottom surfaces sd that it may be reversed, saidframe having spaced parallel beams extending longitudinally of thepallet and joined at their ends by end` plates, said frame heingopenVfor the passage of gases or air therethrough; parallel flangedgrate-supporting structural assemblies removably secured to the tops ofsaid beams and resting thereon with their ends clear of the end platesof the main frame, each said assembly having onelongitudinally-extending structural lower sectio'n resting on andsecured to the beam along which it extends Vby a bolted connection, eachsaid assembly having a longitudinally-extending upper structural sectionwitha horizontal ange: at the top thereof and secured to the lowersection below the anged top by a bolted connection, the upper member o'feach said assembly being thereby connected with the beam along which itextends through anV intervening structural section and through boltedconnectionsat two levels,'the bolted connections at one level havinglongitudinally-elongated bolt holes to enable the upper section toexpand and contract lengthwise relative to the beam along which itextends, and transverse grates extending crosswise of the palletsbetween the flanged uppersections of theassemblies,` the grates havingbifurcated ends engaging the flanges of the upper sections, thegratebars being elongated by the grate-supporting assemblies entirelyabove the top of the main supporting frame.

References Cited in the le ofthis patent UNITED STATES PATENTS t1,098,035 -Greenwalt May 26, 1914 2,434,852 Jackson Jan. 20, 19482,834,593 Hudson May 13, 1958 FOREIGN PATENT-,s

60,1162 Sweden Nov. 23, 1922 719,998 Great Britain Dec. 8, 1954 NITEDSTATES PATENT OFFICE CERTIFICATE OF COBBECTIQN Patent Noe 2,985,440 May23, 1961 Victor E. Koontz 1t s hereby certified that error' appears inthe above numbered patent requiring correction and that the said LettersPatent should read as corrected below.

une 56 and lines 66 and 6T, for "-'vertical each occurrence, readvertical webs 10a --3 line 15, for "11", both occurrences, read 10Column 2, webs 11a", column 3, column 4,

Signed and sealed this 7th day of July 1964.,

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents lines 31 and 32, for "elongated" read elevated

